Two theoretical physicists who suggested that an invisible ocean of energy suffusing space is responsible for the mass and diversity of the particles in the universe won the Nobel Prize in Physics on Tuesday morning. They are Peter W. Higgs, 84, of the University of Edinburgh in Scotland, and François Englert, 80, of the Université Libre de Bruxelles in Belgium.

The theory, elucidated in 1964, sent physicists on a generation-long search for a telltale particle known as the Higgs boson, popularly known (though not among physicists) as the God particle. The chase culminated last year with the discovery of this particle, which confers mass on other particles, at the Large Hadron Collider at CERN, in Switzerland. Dr. Higgs and Dr. Englert will split a prize of $1.2 million, to be awarded in Stockholm on Dec. 10.

“You may imagine that this is not unpleasant,” Dr. Englert said in an early morning news conference.

The Royal Swedish Academy of Sciences had not been able to contact Dr. Higgs, who had vowed he would not be available Tuesday. A friend and fellow physicist, Alan Walker, said in a phone interview on Tuesday morning that Dr. Higgs, who does not use a cellphone or a computer, had gone off by himself for a few days without saying where, and that he would return Friday.

Dr. Higgs, he said, is a modest man who likes his own company and the ability to come and go without a fuss. Even before the announcement, he said, one journalist had invaded Dr. Higgs’s building looking for an interview. “He was sent away with a flea in his ear,” Dr. Walker said.

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In a statement released later by the University of Edinburgh, Dr. Higgs pronounced himself “overwhelmed,” saying, “I hope this recognition of fundamental science will help raise awareness of the value of blue-sky research.”

The prize had been expected ever since physicists working at the Large Hadron Collider announced on July 4, 2012, that they had discovered a particle matching the description of the Higgs. Thousands of particle physicists worked on the project, and for many of them the Nobel is a crowning validation.

Fabiola Gianotti, who led one of the teams at CERN, the European Organization for Nuclear Research, called the prize “a great emotion and a great satisfaction,” adding that it was nice that the experiments were cited in the award. “The young physicists are superexcited.”

The Higgs was the last missing ingredient of the Standard Model, a suite of equations that has ruled particle physics for the last half-century, explaining everything from the smell of a rose to the ping when your computer boots up. According to this model, the universe brims with energy that acts like a cosmic molasses, imbuing the particles that move through it with mass, the way a bill moving through Congress attracts riders and amendments, becoming more and more ponderous and controversial.

Without the Higgs field, many elementary particles, like electrons, would be massless and would zip around at the speed of light. There would be no atoms and no us.

For scientists, the discovery of the Higgs (as physicists call it) affirmed the view of a cosmos ruled by laws of almost diamond-like elegance and simplicity, but in which everything interesting — like us — is a result of lapses or flaws in that elegance. That is the view that emerged in a period of feverish and tangled progress after World War II, in which the world’s physicists turned their energies from war to looking under the hood of nature, using the tools of quantum field theory.

At the heart of this quest was an ancient idea, the concept of symmetry, and how it was present in the foundations of physics but hidden in the world as we experience it. In art and nature, something is symmetrical if it looks the same when you move it one way or another, like a snowflake rotated 60 degrees; in science and math, a symmetry is something that does not change when you transform the system, like the length of an arrow when you turn it around or shoot it.

In 1954, the theorists Chen Ning Yang and Robert L. Mills at the Brookhaven National Laboratory concluded that all fundamental forces were the result of nature’s trying to maintain symmetries — for example, the conservation of electric charge in the case of electromagnetism, or the conservation of momentum and energy in the case of Einstein’s gravity.

By then, however, two more forces of nature had been added to the roster: the so-called weak nuclear force, responsible for some types of radioactive decay, and the strong force, which holds atomic nuclei together. In quantum field theory, forces are transmitted by bundles of energy called bosons. By quantum rules, the mass of a boson is related to the range of the force: the more massive the boson, the shorter its reach.

When the physicist Sheldon Glashow, now of Boston University, wrote down a theory in 1961 that explained the weak force and electromagnetism as manifestations of a single “electroweak” force, the math indicated that the particles that transmitted the nuclear part of that force should be massless, like the photons that transmit light and can spread across the universe. But the nuclear forces barely reach across an atomic nucleus, suggesting that their carriers should be among the most massive of elementary particles. How did the carriers of the weak force become so massive while their brothers the photons remained free and easy?

It was Yoichiro Nambu of the University of Chicago, who would win a Nobel in 2008, who suggested that the fault might lie not in the laws of physics but in how those laws play out in the real world. By a process called symmetry breaking, a situation that started out balanced can wind up unbalanced.

Imagine, for example, a pencil standing on its tip; it will eventually fall over and point only one way out of many possibilities. The mass of the boson can be thought of as the energy released when the pencil falls.

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Scientists at CERN in Switzerland reacted Tuesday to the announcement of the winners of the Nobel Prize in Physics.Credit
Fabrice Coffrini/Agence France-Presse — Getty Images

In 1964, three papers by the different physicists showed how this could work by envisioning a kind of cosmic molasses filling space. Particles trying to go through it would acquire mass.

The first to publish this idea were Dr. Englert and his colleague Robert Brout, who died in 2011. Dr. Englert was born in Etterbeek, Belgium, in 1932, and he studied engineering and physics at the Université Libre de Bruxelles, emerging with a Ph.D. in 1959. While a research associate at Cornell, he bonded with Dr. Brout, a professor there. When Dr. Englert returned to Belgium, Dr. Brout went with him.

While they were working on their paper, Dr. Higgs, a young theorist born in Newcastle-upon-Tyne, England, was working on his own version of the theory.

His paper was rejected by the journal Physics Letters, which was published at CERN, as having no relevance to physics. So he rewrote it and sent it to a rival journal, Physical Review Letters. Along the way he added a paragraph at the end, noting that the theory predicted a new particle, a spinless creature of indeterminate mass, which would become famous as the Higgs boson.

That paper was accepted with the proviso that he mention Dr. Englert and Dr. Brout’s paper, which had beaten him into print by seven weeks.

Meanwhile, three other physicists — Tom Kibble of Imperial College, London; Carl Hagen of the University of Rochester; and Gerald Guralnik of Brown University — were writing their own paper. Just as they were about to send it in, mail that had been delayed by a postal strike came in, containing journals with the other two papers, the one by Dr. Higgs and the one by Dr. Englert and Dr. Brout.

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The Large Hadron Collider at CERN, in Switzerland, which provided crucial research on the Higgs boson, or “God particle.”Credit
Fabrice Coffrini/Agence France-Presse — Getty Images

The groups and their friends have been arguing ever since over exactly who did and said what. In 2004, Dr. Higgs, Dr. Brout and Dr. Englert won the Wolf Prize, considered an important forerunner of the Nobel. In 2010, all six physicists shared the Sakurai Prize of the American Physical Society, another big award. Dr. Brout might logically have shared the Nobel if he were alive today; the prize is not awarded posthumously.

The Higgs boson became a big deal after Steven Weinberg made it the linchpin in a 1967 paper that unified the electromagnetic and weak forces along the lines proposed by Dr. Glashow earlier, earning himself a share of the 1979 Nobel Prize.

Along the way, the Higgs boson achieved a presence in pop culture rare in abstract physics. To the eternal dismay of his colleagues, Leon Lederman, the former director of Fermilab, called it the “God particle” in his book of the same name, written with Dick Teresi. (He later said that he had wanted to call it the “goddamn particle.”) Journalists and the news media could not resist the nickname, however, and many particle physicists grudgingly admitted that the name had brought a dose of drama and public excitement to a field almost breathtakingly austere and abstract.

The July 4 announcement last year ended that tension. That day was also the first time that Dr. Higgs and Dr. Englert had ever met. Indeed, the newly discovered boson so far fits the theoretical predictions so well that physicists are a little dismayed. They were hoping for a surprise or two that would tell them how to improve on the Standard Model.

The award on Tuesday sets the stage for the Swedish academy to figure out someday how to recognize the 10,000 scientists who built the Large Hadron Collider and sifted 2,000 trillion subatomic fireballs for a few dozen traces of the precious godlike particle.

“We are of course thrilled — the first big discovery of the L.H.C., for which we built the giant machine and detectors,” said Maria Spiropulu, a professor at the California Institute of Technology and a member of one of the CERN teams that tracked the Higgs particle down. “For the experimentalists,” she added, “we are kind of used to being excluded from the Nobel.”

A version of this article appears in print on October 9, 2013, on page A1 of the New York edition with the headline: For Nobel, They Can Thank the ‘God Particle’. Order Reprints|Today's Paper|Subscribe